Additive manufacturing technologies, such as 3D printing, have been employed to rapidly produce casting molds as well as end products with complex geometries, e.g., articles requiring undercuts. Binder jetting, a generally lower cost 3D printing process, involves extruding a liquid, or otherwise sufficiently flowable, polymer binder from a nozzle, onto a bed of a particle composition in a controlled manner using a traditional multiple array inkjet print head to form and fuse patterned layers into an article substantially corresponding to a prepared 3D computer model. Machines for 3D binder jet printing of particle compositions are manufactured by companies such as Voxeljet AG, The ExOne Company, LLC, and Zcorp, Inc.
Due to the relative low cost compared to other materials, silica sand has been used as a bound particulate in 3D printing by a growing number of industries to produce molds for final castings, especially for use in casting large metallic components which are prepared by pouring molten metal into a mold cavity formed by a sand casting. However, articles prepared by 3D sand printing have exhibited poor structural characteristics, such as lower flexural strengths, and thus the use of sand has been inadequate for preparing functional parts. Also, the production of large thin-walled sand parts has not been possible due to their high likelihood of breakage during handling.
Thus, improvements are needed to form either or both of stronger and larger thin-walled, low-cost 3D printed articles.